The present invention relates to a method and apparatus for the scanning and processing of workpieces, particularly logs and pieces cut from logs. More particularly, the invention is related to a method and apparatus for the processing of workpieces wherein highly accurate workpiece spatial coordinate information is obtained. Although the invention will be described in connection with the processing of logs or pieces cut from logs, the invention is also applicable to the processing of other types of workpieces, such as in the fabrication of metal workpieces in rolling mills.
A continuing problem in the lumber and plywood industry is the processing of logs to obtain the maximum amount of salable wood products from each log, particularly with regard to the determination of how a log should be optimally divided. Many modern lumber mills now employ some type of automatic scanning equipment which feeds information regarding log, cant, flitch or board dimensions to a data processing device which in turn analyzes the dimensional data to control cutting mechanisms.
A problem in such automatic cutting systems is the provision of continuously accurate workpiece dimensional or spatial coordinate data to the data processing device. Such automatic systems must be operable in the relatively hostile environments of wood products manufacturing facilities subject to temperature fluctuations, moisture and dust. Moreover, the data accuracy is preferably not dependent on continued operator adjustments to the system.
Prior art systems have used a variety of electro-optical techniques for scanning workpieces in automatic cutting systems. One type of such systems has employed a non-coherent light source and photocell sensors either in a fixed array or scanning by means of a rotating mirror. Exemplary of such systems are U.S. Pat. Nos. 3,459,246 (Ottosson); 3,736,968 (Mason); 3,787,700 (Chasson); 3,886,372 (Sanglert) and 3,963,938 (Sanglert).
In U.S. Pat. No. 3,773,422 to Stavis et al, a television camera and laser source are used for calculating dimensions of an object by using known distances and geometric relationships.
U.S. Pat. No. 3,187,185 to Milnes discloses a primarily photographic system for determing the surface contour of an object by viewing the object at an angle from the illuminating light beam. A similar system, using a television camera is set forth in U.S. Pat. No. 3,590,258 to Shibata. Another contour observing system using a light beam and sensor at a separated angle is set forth in U.S. Pat. No. 3,625,618 to Bickel.
Distances to points on an object can be measured by the technique in U.S. Pat. No. 3,610,754 (Perlet), wherein the distance is measured by directing a pulsed laser beam toward the object and measuring the time lapse until the laser illuminated point is received by a television camera.
All of the above patents in their entirety are hereby incorporated by reference.
One problem with prior art systems employing photoelectric cells or other types of solid state sensors is that resolution is relatively poor unless extremely large numbers of sensors are employed. The present cost of such devices makes such a choice unattractive for commercial applications.
In prior art systems employing television type sensors, as well as photoelectric or solid state sensors, accuracy of the readout is a problem due to drifting of the devices caused by component aging, environmental factors and such. Also geometric distortions in the camera or lenses create errors.
A further problem, nut fully addressed by the prior art, is the generation of accurate data by automatic scanning in such a form as to be readily usable by a data processing device for conversion to control signals for automatically processing the workpiece.
It is a general object of the present invention to overcome the disadvantages of the prior art in a system for automatically scanning and processing a workpiece.
It is also a general object of this invention to provide in such a system, a high resolution scanning apparatus and method in which errors in the scanning apparatus are automatically corrected.
Another object of the invention is to provide a method and means for generating signals relating to the dimensions of a workpiece in a form readily handled by data processing equipment.
A further object of the instant invention is to provide a method and means for the accurate processing of workpieces, particularly the accurate dividing of logs or slabs, cants, flitches and boards cut from logs.
Yet a further object is the provision of an automatic workpiece processing system in which the physical relationships among the scanning devices and workpieces are not critical.
These and other objects of the invention will be appreciated as the following description of the preferred embodiment of the invention, and accompanying drawings, are read and understood.